The present invention provides: a composition for silencing a CKAP5 gene, the composition containing, as a drug, double-stranded nucleic acid that has a sequence of bases complementary to a sequence of at least 19 successive bases of mRNA of a CKAP5 gene having an antisense strand of any of SEQ ID NOS: 1-6, and lipid particles that contain a cationic lipid represented by formula (I) (in the formula, R1 and R2 may be the same or different and are a C12-24 linear or branched alkyl, alkenyl, or alkynyl, L1 and L2 may be the same or different and are -CO-O- or -O-CO-, a and b may be the same or different and are 1-3, R3 is a hydrogen atom, C1-6 alkyl, or C3-6 alkenyl) and a pharmaceutical or the like comprising this composition.本發明提供一種含有脂質粒子之抑制CKAP5基因表現之組合物、及含有該組合物之醫藥等,該脂質粒子含有作為藥物之雙鏈核酸與式(I)所表示之陽離子性脂質,該作為藥物之雙鏈核酸之反義鏈具有與序列編號1~6中任一個CKAP5基因之mRNA之連續之至少19個鹼基之序列互補之鹼基序列,(式中,R1及R2相同或不同,為碳數12~24之直鏈狀或支鏈狀之烷基、烯基或炔基,L1及L2相同或不同,為-CO-O-或-O-CO-,a及b相同或不同,為1~3,R3為氫原子、碳數1~6之烷基或碳數3~6之烯基)。
